1. Field of the Invention
The present invention relates to a method and apparatus for managing digital rights of a portable storage device.
2. Description of the Related Art
Recently, digital rights management (DRM) has been actively researched and developed. Commercial services using DRM have already been used or will be used. DRM needs to be used because of the following various characteristics of digital content. Unlike analog data, digital content can be copied without loss and can be easily reused, processed, and distributed, but a large amount of cost, labor, and time are needed to produce the digital content. When the digital content is copied and distributed without permission, a producer of the digital content may lose his/her profit, and his/her enthusiasm for creation may be discouraged. As a result, development of digital content business may be hampered.
There have been several efforts to protect digital content. Conventionally, digital content protection has been concentrated on preventing non-permitted access to digital content, and permitting only people who have paid charges to access the digital content. However, when a person who has paid charges intentionally distributes the digital content to other people, these other people can use the digital content without paying charges. To solve this program, DRM was introduced. In DRM, any one is allowed to freely access encoded digital content, but a license referred to as a rights object is needed to decode and execute the digital content. Accordingly, the digital content can be more effectively protected by using DRM.
A portable storage device is a connectable/disconnectable device such as a portable phone, a computer, or a digital camera which can store data of various types of digital equipment and is portable. The portable storage device includes a storage space for storing data and a portion performing an operation and control. A multimedia card (MMC) is a portable storage device and stores multimedia data to be used for various types of digital equipment, overcoming limitations of conventional hard disks or compact disks. The MMC also includes an operation part that is not included in conventional storage media, thereby having the ability to perform control. As a result, the MMC is suitable to accommodate various kinds of multimedia data in large capacities. Recently, a security function was added to the MMC, thereby developing a secure MMC that secures digital content during storage and transmission and protects copyright. With the development of the secure MMC, rights management on digital content becomes possible in a storage device and digital equipment. Hereinafter, digital equipment such as a digital camera, a portable phone, a computer, and a digital camcorder will be generally referred to as a “device”.
In recent DRM technology, content and a right of using the content are separately transferred. The content is encoded when it is transferred, and the right is needed to use the content. Accordingly, secured custody and management of the right is important. To securely transfer the right, a secure MMC provided with a copy protection or DRM feature is used. According to conventional DRM, independent information regarding the right is not provided to a user, but the user is examined on information regarding the right when the user is about to use the content. Hereinafter, a user means a person possessing a device having a DRM function, and a right means a rights object itemizing a right to play content.
FIGS. 1A and 1B illustrate an example of a structure of a rights object for a secure digital (SD) card, a conventional portable storage device. FIG. 1A illustrates a relation between playlists of audio files. A playlist indicates a single audio file, which may exist at a plurality of tracks in the SD card. To let a user know information on the playlists, a procedure of reading and showing information regarding the playlists is needed. In other words, a storage area of a memory card is accessed to read a file regarding a playlist, and a type of license with respect to particular content can be identified based on the read file. The file has a structure as shown in FIG. 1B.
Referring to FIG. 1B, in the SD card, a title key manager file for audio files is defined as AOBSA1.KEY and includes key information and rights information that are used to decode the audio files existing in a user area of the SD card. POBSP1.KEY denotes a title key manager file for pictures and also includes key information and rights information used to decode the pictures existing in the user area of the SD card. In other words, the title key manager file AOBSA1.KEY includes key information and rights information regarding all of the audio files existing in the user area, and the title key manager file POBSP1.KEY includes key information and rights information regarding all of the picture files existing in the user area.
In the above-described conventional structure, a device needs to directly access a file system of a memory card. Accordingly, the device needs an ability to analyze the file system of the memory card. In addition, part of the memory card is occupied to form and maintain the file structure. Moreover, the memory card is burdened with management of playlists, and a user cannot be supported for convenient playlist configuration.
Such memory cards are suited to applications using a playlist, and therefore, they cannot provide a command providing information regarding a license, i.e., a rights object, existing in the memory cards and regarding content linked to the license and existing the memory cards. Here, the memory cards provide a function that allows track information to be provided through a playlist. However, in this case, playlist management is needed. Since the structure of an SD card is based on a model in which content and a license are transferred together, it is difficult to apply this structure to a DRM model in which a license and content are separately transferred.
FIG. 2 illustrates an example of a structure of a license for a conventional content protection (CP) secure MMC. In the CP secure MMC, rights information is included in a license control area, and Access Control media (ACm) performs access control with respect to media.
A license includes identification information, a transaction identifier (ID), and information regarding access control. A playback count indicates a right to play content based on the license. A move count indicates the number of times that the license can be moved to another device or another storage medium.
Secure MMCs using copy protection or rights management include Memory Sticks made by Sony, SanDisks made by Panasonic, Secure Digital Cards made by Toshiba, and The Content Protection Secure MMC System Specification made by Multimedia Memory Card Association (MMCA). However, they do not consider users' convenience in terms of rights management. In other words, no secure MMCs show kinds of rights stored therein. Accordingly, a user cannot check whether he/she has a right to content until the content in the user's secure MMC is played and cannot prepare appropriate content in advance. In addition, when the secure MMC does not have enough memory to keep a right, when the right is expired, or when the user does not want to use the right any more, there are no methods of easily erasing the right according to the user's selection.
As for an SD card, rights information is divided into only audio, video, and pictures, and a user cannot obtain information regarding his/her rights. As for a CP secure MMC, even a divider for distinguishing audio from video does not exist, and a user cannot obtain information regarding his/her rights, either.
Accordingly, a method of obtaining information regarding a user's right in the user's DRM secure MMC regardless of existence or non-existence of content, obtaining necessary content according to the information, and erasing the right according to the user's selection, thereby allowing the user to manage his/her right, is desired.